Funds are requested to purchase a Rigaku RU-300 X-ray generator, R-AXIS IV image plate system and X-stream cryogenic crystal freezing apparatus, and a Silicon Graphics computer work station to facilitate X-ray crystallographic studies of macromolecules. The existing instrumentation has facilitated a major expansion of crystallographic investigations at the Wistar Institute. This increased activity in structural studies has reached the point where the lack of sufficient instrumentation resources is significantly impeding progress in studying the structures of important macromolecules. The requested instrumentation will provide the resources required to meet the escalating crystallographic demands of the Institute to a major user group composed of 8 laboratories with substantial NIH grant support. These laboratories (Berger, Burnett, Halazonetis, Herlyn, Lieberman, Marmorstein Rauscher, and Speicher) are studying the structure and function of a wide range of macromolecules from nuclear transcription factors and cytoskeletal proteins to whole viruses. The X-ray instrumentation will be housed in the X-ray diffraction laboratory at The Wistar Institute. The instrumentation will be jointly managed by the P.I. (Dr. Ronen Marmorstein) and the Co-P.I. (Dr. Roger M. Burnett). They will be responsible for instrument installation, training, and the day-to-day operational. An internal advisory committee comprised of all major users, and the Associate Director of Science Administration, will oversee equitable access, operation and administration of the instrument. The Wistar Institute is committed to housing, maintaining and staffing the requested instrument for its useful lifetime as verified by an accompanying letter from the Director.